This activity uses paper chromatography as a method of detecting forgeries. Students will use different types of ink from pens to observe how each has an unique chromatogram.
Part 1: Identification of the Authentic Signatures
The purpose of this section is to introduce students to what is a forged signature and through visual comparison of signatures it is sometimes possible to determine if a signature is forged or real. The easiest method to prepare for this part of the activity is to have your signature at the top of a page and then four or five forged signatures written by other people. It is important to have the signatures as close a possible so that it is difficult to determine the differences. This will allow for students to realize other methods are needed. In our school science lab we give out a safety violation ticket everytime someone demonstrates an inappropriate safety behaviour. We used forged safety tickets as an example of forged signatures.
Part 2: Chromatography - Separating Black Ink
In part 2 students learn the how to properly make a chromatogram. Using different pens with black ink, students determine that each ink has an unique chromatogram depending on the combination of ink colours put together to make black. The emphasis in this section is on developing the appropriate technique
Part 3: - The Mystery Note
This section has the students using an unknown ink from a note and comparing the results to their results in part 2. Please remember to tell the students that they must have their piece of note taped to the filter paper with the ink facing the filter paper.
Part 4: What Colours are in the Candy Coating of Smarties
To demonstrate that not only ink can make a chromatogram, students can also rub the coating from candies, such as Smarties®, onto the filter paper. The candy will have to be slightly damp so that the colour from the candy can be transferred onto the filter paper.
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